This invention relates to the art of chairs and, more particularly, to a lift chair for assisting a user when moving between seated and standing positions.
Lift chairs are well known in the prior art. For example, U.S. Pat. No. 5,094,508 (Bathrick et al., hereinafter “Bathrick”) discloses an elevator chair used to assist a user seated in the chair when moving to a standing position. More specifically, Bathrick discloses a lift chair having a first seated position (FIG. 2), wherein a back is substantially vertical and a seat is substantially horizontal, and a second, lift position (FIG. 3), wherein the back remains substantially vertical and a rear portion of the seat pivots upwardly relative to a front portion of the seat to assist the user in standing. Bathrick employs two four-bar mechanisms formed by members 30, 54, 61 and 24 and 31, 55, 61 and 25, respectively. Members 30 and 31 are telescoping. A drive tube 42 moves the back frame assembly 12 up and down, extending and retracting bars 30 and 31 within tubes 18 and 19. The seat 16 pivots as members 30 and 31 move up and down. Bathrick requires the use of relatively complex and expensive components, particularly the drive assembly 14 which includes an externally powered drive motor 40 and drive screw 41.
As a second example of a known lift chair invention, U.S. Pat. No. 3,807,795 (Weant et al., hereinafter “Weant”) discloses a wheelchair having a motor-driven mechanism to move the chair seat, arms and back from a sitting position to a standing position. Weant discloses the seat 25, a lower portion of the back 31, the arms 41 and front arm supports 35 forming four bar linkages such that the seat 25 and arms 41 pivot forward and the back 31 remains generally upright as the chair moves from the seating position (FIG. 8) to the standing position (FIG. 9). Like Bathrick, Weant requires the use of relatively complex and expensive components.
In recognition of the limitations of the existing approaches, the present chair has been developed to provide a lift chair which is mechanically simple and inexpensive to manufacture.